What technology are scientists using to search for other planets? How are they using this technology to identify other planets?

They use radiometry and pyrometry

NASA uses the Transiting Exoplanet Survey Satelite (TESS) telescope that employes this technology

This telescope measures the brightness/luminosity of stars. When this brightness drops regularly, every more or less in the same number of years, then there is the likelihood of a planet orbiting the star. The dip in brightness of the star is directly proportional to the size of the planet and the distance between the star and the orbiting planet.